This invention is concerned with laser diodes, and more specifically with the efficient generation of two opposed and substantially co-linear beams from a single laser diode.
Compact battery-operated laser projectors are used in the construction industry for alignment purposes. The visible beam of light projects a straight line in space which can be used to locate building references. A leveled or plumb beam of light can be used to set the level or plumb directions of building elements such as floors, walls and columns. In many applications a small-diameter visible laser beam replaces a string line. The beam strikes an object producing a small spot of light. The center of the spot may be marked with a pencil as needed. Two co-linear beams are often desired to produce two spots of light which are the end points of a straight line. In a typical application replacing a plumb bob, a spot of light on the floor is located directly below a spot on the ceiling. For example, in U.S. Pat. No. 5,144,487 two co-linear beams are generated using a beam splitter and a mirror. In this case the optical elements must be precisely aligned to produce the required co-linear beams. Other methods of using a beam splitter and subsequent mirrors and glass plates are straightforward but cumbersome. The present invention offers a more compact design which has lower manufacturing cost.